Adjusting weights when changing the type of tanks.

[RIHappyDiver]

When changing the type of tank you’re using, all other things being the same, do you adjust the amount weight based on the full buoyancy difference between the tanks, or the empty?

I’ll be moving from an LP85 to an HP100, but my wife is going from an AL80 to the HP100.

Thanks,
Erik

 

[dedede]

I want to be neutral at the reserve pressure...so based on the buoyancy of the tank when the tank is at reserve pressure.

 

[Bubblesong]

Yes, I added two lbs weight when changing from HP80 to HP65. May need another 1lb for neutral bouyancy at end of dive.

 

[tursiops]

When changing the type of tank you’re using, all other things being the same, do you adjust the amount weight based on the full buoyancy difference between the tanks, or the empty?

I’ll be moving from an LP85 to an HP100, but my wife is going from an AL80 to the HP100.

Thanks,
Erik

Empty.
The amount and weight of gas you carry is a different issue.

 

[Belzelbub]

Absolutely. Look at the empty (or near empty) buoyancy characteristics of the tanks in question. Then adjust accordingly. The weight I carry with my steel 120s would not be enough for my AL80s. variations between manufacturers exist.

Based on the information you provided, I’d expect your wife will have a greater ballast change than you will, though both will be different, as the AL80s are positive when empty. Your gas volume is similar, so the main difference will be in the cylinder.

 

[Fishdip]

When changing the type of tank you’re using, all other things being the same, do you adjust the amount weight based on the full buoyancy difference between the tanks, or the empty?

I’ll be moving from an LP85 to an HP100, but my wife is going from an AL80 to the HP100.

Thanks,
Erik

That is a very big change. I can dive a HP100 with no add weights but need weight for the AL80. It 100% is a pain but adjusting your weight will be far more beneficial then not.

 

[Jcp2]

I think you can take off 2-3 pounds and your wife can take off 4-5 pounds to start to see how it goes.

 

[Gone for diving]

Rule of thumb,
From single alum 80 to steel HP 120.
5lb different, on your weight belt

 

[gmerick]

The weight change is the difference between empty tank buoyancy. My 12l tanks are 1 lb negative when empty. My AL80's are 2 lb positive.
I change by 3 lbs (per tank) when switching. Nothing else matters. You both will change your weight by the tank buoyacy delta when switching as long as the rest of your gear is the same. There is a great buoyancy calculator in the forum that has the tank characteristics.

 

[johndiver999]

The weight change is the difference between empty tank buoyancy. My 12l tanks are 1 lb negative when empty. My AL80's are 2 lb positive.
I change by 3 lbs (per tank) when switching. Nothing else matters. You both will change your weight by the tank buoyacy delta when switching as long as the rest of your gear is the same. There is a great buoyancy calculator in the forum that has the tank characteristics.

This makes no sense to me. You need to adjust lead based on different tanks, the weight difference associated with the different volumes is relatively small.